In the present application the term MEMS sensor is used generically to cover a microelectronic and microelectromechanical system having mechanical elements (usually on a single chip) with minute physical dimensions in the micro- as well as nano-meter range. As such, the term is also meant to cover nanosensors and other similar devices.
MEMS sensors are made in various configurations for sensing certain physical instantaneous parameters such as acceleration, magnetic field direction and intensity, etc. MEMS sensors have wide range uses including such diverse systems as accelerometers triggering air bags in automotive applications, electronic compasses, GPS navigational subsystems in mobile devices, etc. Typically, these sensors generate measurements that are either scalars or multidimensional vectors. For example, both acceleration and magnetic fields are expressed as three-dimensional vectors, and hence, the respective sensors generate multidimensional outputs.
It is well known that MEMS outputs are generally nonlinear responses to inputs and must be calibrated for these non-linear effects using appropriate coefficients. Moreover, the MEMS response is not stable over time but changes frequently in response to environmental variations, and these changes produce environmental artifacts in the MEMS outputs that must be eliminated by recalibrating the outputs. In other words, the outputs of MEMS are not reliable unless they are frequently checked and recalibrated to eliminate environmental artifacts to match or compensate for environmental and ambient changes.
The processes necessary to recomputed the calibration coefficients can be fairly complicated, especially for multi-dimensional sensors, requiring complex matrix operations. Therefore each recalibration slows down and even suspends the process of obtaining the requirement measurements from the sensor. Moreover, when the MEMS are incorporated into mobile or portable devices, such recalibrations use up valuable resources within the portable device, including microprocessor time, and power. This last consideration is especially important in battery operated devices. One environmental effect that consistently requires the recalibration of the outputs of MEMS is temperature variation.
Accordingly there is a need to provide a simpler, faster and less energy consuming way of recalibrating the outputs of MEMS sensors, especially to compensate for temperature variations.